1. Field of the Invention
The present invention relates to a fastening element having a stem with a tip at one of its ends and head arranged at an end of the stem opposite the tip, with the stem having a first spherical section extending from the tip in the direction of the head, and a second section adjoining the first section at an end of the first section remote from the tip and extending in the direction of the head, and a thread profile provided on the stem.
2. Description of the Prior Art
Fastening elements of the type described above, such as nails, bolts and the like are usually formed of steel and are used, in fastening technology for securing objects to hard materials such as concrete, metal, and stone. The drive-in process of such fastening elements is carried out with high speed, and the fastening elements are driven-in percussively or otherwise, e.g., with combustion-driven tools.
German Publication DE 101 19 800 A1 discloses a fastening element having a head and a stem adjoining the head and provided, at its end remote from the head, with a tip. The stem has a first spherical section that tapers toward the tip, and a second section that adjoins the first section and extends in the direction toward the head. The spherical first section and the following second section are provided, at least partially, with a knurl profile. This profile increases friction and, therefore, abrasion of the material.
U.S. Pat. No. 5,127,785, from which the present invention proceeds, discloses a nail for suspending of supports and that has a stem having a first bullet-shaped or spherical section decreasing toward the tip, and a second cylindrical section. The head, which is provided at the end of the stem remote from the tip, has the same diameter as the second cylindrical section. The stem is provided with a deeply cut-in thread profile that ends in front of the tip and that only partially surrounds the rear stem region. The thread serves for removal of the material produced by the drivable-in nail and increases the friction between the nail and the constructional component.
The drawbacks of such fastening element consists in that with thread grooves having the same depth and with an intermediate gradient, at a very rapid drive-in displacement, which is carried out, e.g., with a combustion-driven setting tool, the thread does not lead to rotation of the nail but rather acts as a grater, causing substantial abrasion. The abrasion reduces the holding forces of a nail in the constructional component.
Accordingly, an object of the present invention is to provide a fastening element in which the foregoing drawbacks are eliminated.
Another object of the present invention is to provide a fastening element with good holding characteristics in a hard material, e.g., concrete or steel.